Space Elevator

[Brian H]

Aeronaut wrote: I intend to fully integrate the law of unintended consequences. But much as I would love to reach a full consensus, I’m not fool enough to believe that I will ever see one, or that in practice it’s really a good thing. That puts the leverage in the late adopters’ hands- the current power structure which we have to reach many working agreements with along the way. Thankfully there will be an adoption gradient of at least 10 years, no matter how fast FF’s can be made, sold, and installed, which will help all parties see that the trend is irreversible.

Now, I want you to pay very close attention, Brian. Aneutronic Fusion is only the power source for the future that I see unfolding. By pre-selling a million of them, my organization can develop and deploy at least one space elevator. That convergence zone is the sweet spot that I’m aiming at.

If you want to make sense, like you often did last year, please feel free to do so. Otherwise, I move that we cap this thread.

10 years will only make a good beginning on digesting and exploiting the consequences of FF. I’m fairly imaginative, but this spins way beyond what I can project.

As for the space elevator, I’m a big fan, but still don’t think the tether material problem is in hand; even carbon fiber is looking too weak. Swinging a small asteroid on the end of a 71,000 km string is no joke! (the center of gravity of the rig has to be in geosynch position, about 31,800 km up.)

[Aeronaut]

I’m of the understanding that raising ~$50G is the most important challenge to solve. I’ve rephrased it to raising $50G without Wall Street or government funding, btw.
I just wish it would work around 40 degrees either side of the equator so I could put one over Lake Michigan.

[emmetb]

That would be so cool. If we could have a space elevator! Of course that would be: the future of mankind/life on earth (in the galaxy? universe?) hanging by a nanofiber thread? 😉

Still, why not! And, at the same time, let’s do the directed panspermia thing, as an insurance policy.

By the way, is there such a thing as an “active” space elevator? I imagine the cable having thrusters at regular intervals to relieve the stress on the cable. FF would be perfect for this.

[Brian H]

$50G? is that Gigabucks? An elevator would cost a small fraction of that. If you’re talking about listing costs and capital for an exchange, $50 thousand sounds very low.

[Aeronaut]

Less cost, mo’ betta! I’ve seen guesstimates ranging from $10G to $50G, but I’d like to stress that I’ve never seen anything detailing how those numbers were arrived at. My guess is that the anchoring vessel would be around 130,000 tons displacement, and would take the lion’s share of the budget and possibly the lead time. If anybody’s seen any relevant numbers, I’d greatly appreciate a link to them.

The design I’ve seen proposed allows for around 30 tons per car, which could allow for a 5MW climbing motor, depending on the cooling system’s ability to handle the transition from sea level atmosphere to zero vacuum and gravity in the span of around 30 minutes. I’d hate to see the cooling system eat up the freight mass budget.

[Aeronaut]

Listing costs and control issues make listing an IPO a living hell. Think of it as asking a LOT of people that you don’t really have to, for permission to do something that they don’t think is possible. Plus the entire paranoia mindset that these people might be shopping your idea behind your back. Far more productive to spend that time building your brand.

The net result is that the sales psychology is reversed, as Google did with their IPO, and you can shave 100s of thousands off the listing costs, while setting the terms wherever you damn well please, since it’s a privately held company that is not required to list, if its core competency is in selling info-products and services.

If an elevator really does cost that much, this can be a good place for a properly planned and executed IPO. But post-elevator, with millions of FFs in service, is the real place to cash in. Until then, the money is a tool which reflects my organization’s ability to remove the word fiction from the label science fiction in a timeframe which defies most peoples’ imaginations.

And makes it look deceptively simple, of course.

[Brian H]

I seem to recall seeing that the Japanese had an ongoing project to put up an elevator (fairly soon?) for about $10Bn. But not sure how current that info is.

OK, here’s a report:

Japan is increasingly confident that its sprawling academic and industrial base can solve those issues, and has even put the astonishingly low price tag of a trillion yen (£5 billion) on building the elevator. Japan is renowned as a global leader in the precision engineering and high-quality material production without which the idea could never be possible.

In Ameribux that’s ~$11Bn at current rates.

You have a couple of weeks to get to Redmond, home of MS:

http://spaceelevatorconference.org/default.aspx

[Brian H]

emmetb wrote: That would be so cool. If we could have a space elevator! Of course that would be: the future of mankind/life on earth (in the galaxy? universe?) hanging by a nanofiber thread? 😉

Still, why not! And, at the same time, let’s do the directed panspermia thing, as an insurance policy.

By the way, is there such a thing as an “active” space elevator? I imagine the cable having thrusters at regular intervals to relieve the stress on the cable. FF would be perfect for this.

Sounds technically possible, though what mass the thrusters would use, I’m not sure. Also, it would be a “cute” computation problem, as the closer to the ground, the more the cable segment would want to speed up to stay in orbit, so the thruster exhaust would be mostly forward (i.e., pushing the cable back, slowing it down).

Some of the descriptions of elevators posit that the top of the structure is the station itself in geosychronous orbit, but I don’t think that’s possible. That’s the point where there is a perfect balance of speed and gravity, so the center of mass must be there, only achievable (I think) if either the station is HUGE (an orbited asteroid?), or the length of cable below tending to tug the station forward (faster) and down is balanced by an equal length above, tending to tug it upwards and back (slower).

Orbital mechanics is a beach!

[Aeronaut]

Good backgrounder, dated 10/2008.

The model I remember posits a 69,000 mile tether with a very small counterweight. The appeal to me is that it can use this as a thrustless ballistic launch system – a headstart for ion thrusters- thus relieving the ship’s designers and operators from the delta-vee constraints of escaping Earth’s gravity for round trip vessels.

We’re going to need to move this branch of the thread to its own, new thread, btw.

[KeithPickering]

The biggest technical challenge may not even be cable strength. It will be impact resistance/avoidance from gazillions of pieces of junk in Low Earth Orbit. A paint fleck at 17,000 mph can ruin your whole day. Shuttle damage is trivial by comparison, since the shuttle tends to travel in the same direction as other LEO objects, lessening the relative velocity. The cable for a space elevator isn’t moving at orbital speed until you’re up at 22,000 miles. Take a look at this diagram:

Now imagine having to move the cable bottom to avoid each and every one of those little dots, simultaneously. And those dots are all moving! Clearly it’s an impossible task. But if you don’t do it, your cable takes impacts. So how long can the cable survive under such bombardment? Not long, is the guess here. And the problem is only going to get worse as time goes on and more and more junk ends up in orbit.

[Aeronaut]

Sounds like somebody needs to invent a vacuum cleaner 😆

[Brian H]

KeithPickering wrote: The biggest technical challenge may not even be cable strength. It will be impact resistance/avoidance from gazillions of pieces of junk in Low Earth Orbit. A paint fleck at 17,000 mph can ruin your whole day. Shuttle damage is trivial by comparison, since the shuttle tends to travel in the same direction as other LEO objects, lessening the relative velocity. The cable for a space elevator isn’t moving at orbital speed until you’re up at 22,000 miles. Take a look at this diagram:

Now imagine having to move the cable bottom to avoid each and every one of those little dots, simultaneously. And those dots are all moving! Clearly it’s an impossible task. But if you don’t do it, your cable takes impacts. So how long can the cable survive under such bombardment? Not long, is the guess here. And the problem is only going to get worse as time goes on and more and more junk ends up in orbit.

I gots tha ansar!

Surround the cable with a braced hollow tube, about 0.5km internal space and .2km thickness of walls, of aerogel. It is insanely light and strong, and would be readily patchable with external extruder-spider thingies crawling up and down non-stop.

All fiksed!

(But I admit, it would definitely ruin the view for the cable passengers going up and down! Maybe laser light shows on the inner surface (or other effects from luminescent gizmos embedded in the gel? 😉 ) )

[Brian H]

KeithPickering wrote: The biggest technical challenge may not even be cable strength. It will be impact resistance/avoidance from gazillions of pieces of junk in Low Earth Orbit. A paint fleck at 17,000 mph can ruin your whole day. Shuttle damage is trivial by comparison, since the shuttle tends to travel in the same direction as other LEO objects, lessening the relative velocity. The cable for a space elevator isn’t moving at orbital speed until you’re up at 22,000 miles. Take a look at this diagram:

Now imagine having to move the cable bottom to avoid each and every one of those little dots, simultaneously. And those dots are all moving! Clearly it’s an impossible task. But if you don’t do it, your cable takes impacts. So how long can the cable survive under such bombardment? Not long, is the guess here. And the problem is only going to get worse as time goes on and more and more junk ends up in orbit.

I gots tha ansar!

Surround the cable with a braced hollow tube, about 0.5km internal space and .2km thickness of walls, of aerogel. It is insanely light and strong, and would be readily patchable with external extruder-spider thingies crawling up and down non-stop.

All fiksed!

(But, I admit, it would definitely ruin the view for the cable passengers in transit! Maybe laser light shows on the inner surface (or other effects from luminescent gizmos embedded in the gel? 😉 ) )

[Aeronaut]

That could shield the tether, but how would the drive wheels get their traction?

[emmetb]

Now imagine having to move the cable bottom to avoid each and every one of those little dots, simultaneously. And those dots are all moving! Clearly it’s an impossible task. But if you don’t do it, your cable takes impacts. So how long can the cable survive under such bombardment? Not long, is the guess here. And the problem is only going to get worse as time goes on and more and more junk ends up in orbit.

This really seems like a show-stopper for the pace elevator. Also its seems a practical space-elevator system needs some active daming to keep it from vibrating due to winds, tidal forces, etc. That all seems to make it highly impractical.

These guys have an interesting alternative concept:
http://www.tethers.com/LaunchAssist.html

How about changing their concept slighty: make the tether active at the top by employing a FF driven electric reel. This means you add additional lifting capacity by shortening the cable as the payload is ascending (a bit like an ice-dancer drawing the arms closer the the body to pick up angular velocity).Of course you can only draw the tether in slightly before reaching appex, but it still might have an effect. If it doesn’t then at least it is important to keep retracting the ribbon after launch in order to minimize the time of exposure of the tether to impact from space-debris.

In between launches, FF propulsion can be used to restore the orbit of the tether facility.

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